Scleroderma (SSc) is an autoimmune disease of unknown etiology characterized by endothelial cell injury and tissue fibrosis. Considerable body of evidence indicates that the vascular disease in SSc precedes, and may well be, a driving force behind enhanced biosynthetic activity of fibroblasts. To better understand the molecular events, which operate in the pathogenesis of SSc, we have undertaken an investigation of gene expression in microvascular endothelial (MVEC) cells isolated from involved and uninvolved skin of patients with diffuse systemic sclerosis. Preliminary data indicate that MVEC derived from unaffected and affected skin of SSc patients exhibit qualitatively similar aberrations in the constitutive expression of certain pathogenically relevant genes when compared with MVEC of sex- and age-matched normal volunteers. The main goal for the current proposal is to explore the basis for the development of the aberrant EC phenotype in SSc. Understanding disease related process that leads to endothelial dysfunction may provide insights into pathogenic processes associated with scleroderma and may help in the design of future therapeutic intervention. The three specific aims for the proposal are: 1. To study SSc MVEC gene expression phenotype under different experimental conditions, particularly under mechanical shear stress forces, to examine the persistence of the phenotype. 2. To investigate the possibility that SSc MVEC phenotype may result from an, in vivo. DNA methylation, and that cytotoxic T cells may play a role in this process. 3. To explore the possibility that SSc MVEC phenotype results from, in vivo, selection through clonal expansion of a heterogeneous population of EC. Involvement of the vascular endothelial cells is a major event in the pathogenesis of scleroderma. Our longterm goal is to precisely define the mechanisms leading to endothelial dysfunction and to investigate potential therapy that may help in preventing or modifying the vascular abnormalities.